Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$73.45	11.662%	$82.0157	$82.02	$82.00	$82.00
Purchase #2	$20.83	4.562%	$21.7803	$21.78	$21.80	$21.80
Purchase #3	$113.49	9.397%	$124.1547	$124.15	$124.15	$124.20
Purchase #4	$136.58	10.524%	$150.9537	$150.95	$150.95	$151.00
Purchase #5	$55.96	4.550%	$58.5062	$58.51	$58.50	$58.50
Purchase #6	$223.55	9.619%	$245.0533	$245.05	$245.05	$245.10
Purchase #7	$171.66	11.155%	$190.8087	$190.81	$190.80	$190.80
7 purchase totals =	$795.52		$873.2726	$873.27	$873.25	$873.40